Methods and devices for draining fluids and lowering intraocular pressure

ABSTRACT

Methods, devices and systems for draining fluid from the eye and/or for reducing intraocular pressure. A passageway (e.g., an opening, puncture or incision) is formed in the lamina cribosa or elsewhere to facilitate flow of fluid from the posterior chamber of the eye to either a) a subdural location within the optic nerve or b) a location within the subarachnoid space adjacent to the optic nerve. Fluid from the posterior chamber then drains into the optic nerve or directly into the subarachnoid space, where it becomes mixed with cerebrospinal fluid. In some cases, a tubular member (e.g., a shunt or stent) may be implanted in the passageway. A particular shunt device and shunt-introducer system is provided for such purpose. A vitrectomy or vitreous liquefaction procedure may be performed to remove some or all of the vitreous body, thereby facilitating creation of the passageway and/or placement of the tubular member as well as establishing a route for subsequent drainage of aqueous humor from the anterior chamber, though the posterior chamber and outwardly though the passageway where it becomes mixed with cerebrospinal fluid.

RELATED APPLICATION

[0001] This application claims priority to U.S. Provisional PatentApplication No. 60/447,999 filed on Feb. 18, 2003, the entirety of whichis expressly incorporated herein by reference.

FIELD OF THE INVENTION

[0002] This invention relates generally to medicine and surgery, andmore particularly to methods and devices for lowering intraocularpressure in human or veterinary patients.

BACKGROUND OF THE INVENTION

[0003] In normal adults the ocular globe is approximately spherical,with a diameter averaging 24.5 mm. The cornea is a transparent tissueinserted into the sclera at the limbus, the anterior chamber is behindthe cornea. The iris is the anterior extension of the ciliary body, itpresents as a flat surface with a centrally situated round aperture, thepupil. The iris lies in contiguity with the anterior surface of thelens, dividing the anterior chamber from the posterior chamber, each ofwhich contains aqueous humor. The lens is a biconvex, avascular,colorless and almost completely transparent structure about 4 mm thickand 9 mm in diameter. The lens is suspended behind the iris by thezonules, which connect it with the ciliary body. Anterior to the lens isthe aqueous humor and posterior to the lens is the vitreous. The“vitreous body” which occupies approximately four fifths of the cavityof the eyeball, behind the lens. The vitreous body is formed ofgelatinous material, known as the vitreous humor. Typically, thevitreous humor of a normal human eye contains approximately 99% wateralong with 1% macromolecules including: collagen, hyaluronic acid,soluble glycoproteins, sugars and other low molecular weightmetabolites.

[0004] The retina is essentially a layer of nervous tissue formed on theinner posterior surface of the eyeball. The retina is surrounded by alayer of cells known as the choroid layer. The retina may be dividedinto a) an optic portion which participates in the visual mechanism andb) a non-optic portion which does not participate in the visualmechanism. The optic portion of the retina contains the rods and cones,which are the effectual organs of vision. A number of arteries and veinsenter the retina at its center, and splay outwardly to provide bloodcirculation to the retina. The posterior portion of the vitreous body isin direct contact with the retina. Networks of fibrillar strands extendfrom the retina and permeate or insert into the vitreous body so as toattach the vitreous body to the retina.

[0005] The optic nerve provides communication between the retina and thebrain. The optic nerve is primarily composed of axons from the retinalganglion cells along with glial support cells and other tissue. Theoptic nerve begins at the optic nerve head or disc and passes throughthe sclera in the area of the lamina cribrosa. The optic nerve thenpasses through the orbit and optic canal to the optic chiasm. Posteriorto the lamina cribrosa, the optic nerve is surrounded by a three-layeredmeningeal sheath similar to the central nervous system which consists ofa dura mater (optic nerve sheath), arachnoid mater, and pia mater. Thesubarachnoid space surrounding the optic nerve is in directcommunication with the subarachnoid space of the central nervous system.

[0006] The term “glaucoma” encompasses a group of diseases that causeprogressive damage to the optic nerve and resultant optical fielddefects, vision loss and, in some cases, blindness. Glaucoma istypically, but not always, accompanied by abnormally high intraocularpressure. There are three basic types of glaucoma—primary, secondary andcongenital. The primary type of glaucoma is most common. Cases ofprimary glaucoma are classified as either open angle or closed angle.Secondary glaucoma occurs as a complication of a variety of otherconditions, such as injury, inflammation, vascular disease and diabetes.Congenital glaucoma is elevated eye pressure present at birth due to adevelopmental defect in the eye's drainage mechanism.

[0007] As well as being an important marker of the presence andadvancement of glaucoma, the structure of the optic nerve head may playa role in the pathogenesis of glaucoma. Two main theories exist for themechanism of optic nerve damage in glaucoma. One theory, known as themechanical IOP related theory, suggests that the pressure head actsdirectly on the lamina cribosa. The lamina cribosa is not well supportedsuperiorly and inferiorly at the disk and, as a result, initial damageoccurs superiorly and inferiorly to produce the characteristic arcuatedefects. Variations in the ganglion cell support at the disk may explainthe variations between IOP susceptibilities of individuals with similarIOP's. The second theory, known as the vascular mechanism of damagetheory, suggests that changes occur within the microcirculation of thedisk capillaries and such microvascular changes are responsible forglaucomatous changes.

[0008] Irrespective of the type of glaucoma a patient suffers from,controlling IOP through the use of drugs and/or surgery is a mainstay oftreatment. It is generally acknowledged that lowering intraocularpressure in glaucoma patients can prevent or lessen the irreversibleglaucoma-associated destruction of optic nerve fibers and the resultantirreversible vision loss.

[0009] Presently the use of topically applied glaucoma medicationsconsisting of mainly beta blockers, prostaglandin analogues, alpha-2agonists, and carbonic anhydrase inhibitors are short acting, prone todeleterious side effects, prone to compliance issues, and must be usedfor life. Also, at present, the use of argon laser trabeculoplasty as ameans for treating glaucoma is limited in clinical response, lasts onlyapproximately 1-2 years, and is limited by the number of applicationsper eye. Also, at present, the performance of trabeculectomy procedureswith or without antimetabolites allows for the external drainage ofaqueous humor from the eye. However, trabeculectomy procedures can betechnically difficult, frought with early hypotony, late failure, andhigh rate of endophthalmitis leading to permanent loss of the eye.

[0010] Another surgical approach to the treatment of glaucoma involvesthe implantation of a shunt to drain aqueous humor from the anteriorchamber of the eye. Examples of glaucoma shunts of the prior art includethose described in the following U.S. Pat. No. 5,626,558 entitled“Adjustable Flow Rate Glaucoma Shunt and Method of Using Same;” No.6,007,510 entitled “Implantable Devices and Methods for Controlling theFlow of Fluids Within the Body;” No. 6,007,511 entitled “Shunt Valve andTherapeutic Delivery System for Treatment of Glaucoma and Methods andApparatus for its Installation;” No. 6,142,969 entitled “SuturelessImplantable Device and Method for Treatment of Glaucoma” and No.6,626,858 entitled “Shunt Device and Method for Treating Glaucoma.” Theentire disclosure of each of these United States patents is expresslyincorporated herin by reference.

[0011] Thus, there remains a need in the art for the development of newmethods and apparatus for lowering IOP and/or for draining fluid fromthe posterior chamber of the eye for treatment of glaucoma or otherdisease states.

SUMMARY OF THE INVENTION

[0012] The present invention provides devices and methods for drainingfluid from the posterior chamber of the eye into the optic nerve and/orthe subarachnoid space. The posterior chamber of the eye is in directfluidic communication with the anterior chamber of the eye. Thus, themethods and devices of the present invention may be used to treatdiseases that are characterized by excess production and/or impaireddrainage of aqueous humor (e.g., glaucoma) as well as othervitreoretinal disease states (e.g., for clearance of vitreoushemorrhage).

[0013] In accordance with the invention, there is provided a method fordraining fluid from the posterior chamber of the eye by creating apassageway between the posterior chamber of the eye and either i) alocation within the optic nerve or ii) a location within thesubarachnoid space. Contiguous communication between the anteriorchamber, posterior chamber and subarachnoid space may be achieved byadditionally performing either a) complete or partial surgical removalof the vitreous humor (e.g., a vitrectomy) or b) liquefaction of all ora portion of the vitreous humor (e.g., pharmacologic vitreolysis byintravitreal administration of urea; a urea derivative; a compoundhaving a urea group; hyaluronidase or any other enzyme or agent thatcauses vitreal liquefaction). The passageway by which the fluid drainsfrom the posterior chamber into the subarachnoid space may simplycomprise a hole or puncture made in the lamina cribosa or other suitablelocation. Alternatively, the passageway may comprise a tubular shuntdevice that is implanted so as to drain fluid from the posterior chamberinto the optic nerve or into the subarachnoid space. Fluid which firstdrains into the optic nerve will diffuse into the subarachnoid spacewhere it becomes mixed with CSF. Fluid which drains directly into thesubarachnoid space will mix with CSF within the subarachnoid space. Inapplications of the method wherein a shunt device is employed, the shuntdevice may alternatively extend between the anterior chamber andsubarachnoid space such that it bypasses the posterior chamber orvitreous cavity (i.e., the shunt device may extend through asubconjunctival or subscleral tunnel), furthermore the shunting devicemay also incorporate a system of communication between the anteriorchamber and subarachnoid space that bypasses the vitreous humor bypassing directly through it (e.g., a tube that extends through thevitreous body).

[0014] Further in accordance with the invention, there is provided ashunt device for draining fluid from the posterior chamber of the eyeinto the optic nerve or subarachnoid space. Such shunt device comprisesa tube having a proximal end, a distal end and a lumen extendinglongitudinally therethrough, a substantially tissue penetrating tip onthe distal end of the tube, a plurality of openings formed at or nearthe distal end of the tube to allow fluid to drain out of the lumen ofthe tube and at least one tissue engaging member configured to allow theshunt device to be advanced, tip member first, into tissue but to engagesaid tissue in such a manner as to subsequently deter retraction of theshunt out of the tissue. Optionally, the shunt device may additionallyinclude a pressure control and/or one-way valve to control the magnitudeof the pressure head required to cause fluid to drain from the eyethrough the shunt device and/or to prevent unwanted backflow of fluidinto the eye through the shunt device. Also, optionally, the shuntdevice may comprise a shielding member, such as a semi-permeablemembrane, to prevent or deter clogging of the shunt device by foreignmatter and or tissue in-growth.

[0015] Still further in accordance with the present invention, there isprovided a system that comprises a shunt device of the above-describedcharacter in combination with an introducer that is insertable into theeye and useable to implant the shunt device at its desired implantationposition within or adjacent to the optic nerve. Such introducer maycomprise a tubular cannula through which the shunt device may be passedand/or an elongate member which may be used to drive or advance theshunt device to its intended location. In some embodiments, the elongatemember may be used without the tubular cannula. In other applications,the shunt device will be initially loaded into the lumen of the tubularcannula and the elongate member (e.g., a solid or tubular pusher rod)may be used to push the shunt device out of the distal end of thecannula and to its intended site of implantation.

[0016] Further aspects and elements of the present invention will becomeapparent to those of skill in the relevant art upon reading andconsidering the following detailed description and the accompanyingdrawings to which it refers.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is a longitudinal sectional view of one embodiment of anocular shunt implantation system of the present invention.

[0018]FIG. 1A is a perspective view of the cannula component of theocular shunt implantation assembly of FIG. 1.

[0019]FIG. 1B is a perspective view of the shunt component of the ocularshunt implantation assembly of FIG. 1.

[0020]FIG. 1B′ is a partial cut-away/sectional view of a shunt device ofthe present invention incorporating an optional one-way valve to deterbackflow and optional shielding member (e.g., a semi-permeable membrane)to deter clogging of the shunt due to debris or cellular tissueingrowth.

[0021]FIG. 1C a perspective view of the pusher component of the shuntimplantation assembly of FIG. 1.

[0022]FIG. 2A is a cross-sectional view of a human eye into which anocular shunt implantation system of the present invention has beeninserted and positioned for advancement/implantation of the shunt.

[0023]FIG. 2B is a cross-sectional view of a human eye into which anocular shunt of the present invention has been implanted to shunt fluidfrom the posterior chamber of the eye into the body of the optic nerve.

[0024]FIG. 2C is a cross-sectional view of a human eye into which anocular shunt of the present invention has been implanted to shunt fluidfrom the posterior chamber of the eye into the area outside of the opticnerve.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0025] The following detailed description and the accompanying drawingsare provided for the purpose of describing certain non-limiting examplesor embodiments of the invention only. This detailed description is notintended to describe all possible examples and embodiments of theinvention and, thus, shall not limit the scope of the claimed inventionin any way.

[0026]FIGS. 1-1C show one embodiment of a system 10 for implantation ofa shunt device 12 in accordance with the present invention. This system10 generally comprises the shunt device 12, a cannula 14, and a pusher16. As shown in FIG. 1, the shunt device 12 is initially positionedwithin the lumen 18 of the cannula 14 and the pusher 16 is positioned inthe lumen 18 of the cannula 14 behind the shunt device 12 such that thepusher 16 may be used to push the shunt device 12 out of the distal endDE of the of the cannula 14. One way of performing this shunt-expulsionprocedure is shown in FIG. 2A and is explained in detail hereblow.

[0027] The particular embodiment of the shunt 12 shown in FIG. 1Bcomprises a tube 22 having a lumen 24 extending longitudinallytherethrough. A tip member 26 is positioned on the distal end of thetube 22. The tip member 26 of this embodiment is generally conical inshape, but it will be understood that the tip member may be beveled,tapered, trocar tipped or of any other shape that will allow it toadvance through tissue as explained herebelow. Apertures 28 are formedin the side wall of the tip member 26 to allow fluid to drain out of thelumen 24 of the tube 22. Optional tissue engaging members 30, such asbarbs, hooks, undercuts, adhesive regions, tissue in-growth receivingareas, etc., may be formed on the shunt 12 to deter unwanted movement orretraction of the shunt 12 after it has been advanced to its intendedimplantation position. Also, optionally, a flange (e.g., any laterallyextending member or area or increased diameter) may be formed on theproximal end of the tube 22 to engage the lamina cribosa or other tissuein a manner that deters advancement of the tube beyond its intendedposition. The shunt device 12 may have a diameter or cross-dimension atits widest point of about 1 micron to about 2000 and preferably of about50 microns to about 400 microns.

[0028]FIG. 1B′ shows an alternative embodiment of the shunt device 12 awhich has the same construction as the shunt device 12 shown in FIG. 1Bbut additionally includes an optional one way valve 23 and an optionalshielding member 29 which covers the apertures 28 to prevent or deterthe entry of foreign matter or issue ingrowth through apertures 28. Theone way valve 23 serves to allow fluid flow in the distal direction(Arrow DD) while preventing or substantially deterring backflow in theproximal direction (Arrow PD). The one way valve may be a duckbill typevalve comprising a plurality of flexible leaflets 25, as shown, or maycomprise any other suitable type of check valve or one-way valve, suchas a ball type check valve, a flapper, or any of the valves typicallyused as hemostatic valves on small medical catheters of a size similarto this shunt device 12 a. Also, this one-way valve 23 may beconstructed to open only when the pressure of fluid within the lumen 24proximal to the valve 23 exceeds a predetermined maximum, therebyproviding for control of the intraocular pressure and preventing thedrainage of too much fluid from the eye as may result in hypotony orother untoward sequale.

[0029] The cannula 14 may comprise a tube having a generally cylindricalwall 14, a lumen 18 extending longitudinally therethrough between anopen proximal end PE and an open distal end DE.

[0030] The pusher 16 may comprise a solid or tubular elongate member 34having a proximal end PE and a distal end DE. Optionally, a handle 38may be positioned on the proximal end of the elongate member 34. Also,optionally, the elongate member 34 may have an outer diameter that issized to be received within the lumen 24 of the shunt device 12 and thedistal end DE of the elongate member 34 may be tapered, as shown in FIG.1C, to seat within the tapered tip member 26 of the shunt device 12.

[0031] Some or all of the components of the system 10 may be formed ofsilicon, polyethylene, polypropylene, polycarbonate, stainless steel orother biologically compatible materials. In the particular embodiemtshown in the figures, the shunt device 12 or 12 a may be substantiallyformed of silicon material. The shunt device 12 or 12 a may also involvean active pumping system or may incorporate a wick like system to movefluid in the required direction.

[0032]FIG. 2A-2C show the system of FIGS. 1-1C in its currently intendedmode of operation. Prior to implantation of the shunt device 12 or 12 a,a vitrectomy device may be inserted into the posterior chamber PC and avitrectomy performed to remove at least a portion of the vitreous bodyfrom the posterior chamber PC. Alternatively, all or a portion of thevitreous body may be liquefied. Such vitreal liquefaction may beaccomplished by intravitreal administration (e.g., intravitrealinjection) of one or more agents that cause liquefaction of the vireoushumor. Examples of such agents include but are not limited to; urea,urea derivatives, compounds having urea groups, hyaluronidase and otherenzymes or other substances that cause vitreal liquefaction.Descriptions of these and other substances that cause vitrealliquefaction, as well as dosage information and associated methods foradministration, are found in U.S. Pat. No. 5,292,509 (Hagman): U.S. Pat.No. 6,551,590 (Karageozian et al.); U.S. Pat. No. 6,610,292 (Karageozianet al.) and U.S. Pat. No. 6,462,071 (Karageozian et al., the entiretiesof which are expressly incorporated herein by reference.

[0033] As shown in FIG. 2A, a small opening such as a needle puncture ismade in the pars plana PP and the system 10 of the present invention isinserted through that opening and through a region of the poster chamberPC from which the vitreous body has been removed (e.g., by vitrectomy)or in which the vitreous body has been liquefied (e.g., by intravitrealinjection of a vitreous liquefying agent as described above). The system10 is advanced to position where the distal end DE of the cannula 14 ispositioned immediately anterior to the lamina cribosa. The pusher 16 isthen advanced in the distal direction (Arrow DD) while the cannula 14 isheld stationary, thereby pushing the shunt device 12 or 12 a out of thedistal end DE of the cannula 14 and causing the distal tip member 26 ofthe shunt device 12 or 12 a to penetrate through the lamina cribosa andoptic nerve ON tissue. The pusher 16 is advanced until resistance isfelt due to the impingement of the flange member 32 of the shunt device12 or 12 a with the optic nerve head. At this point, the shunt member 12or 12 a has been advanced to its intended implantation site and thepusher 16 and cannula 14 may be removed from the eye, leaving the shuntdevice 12 or 12 a in place. Depending on the angle at which the shuntdevice 12 or 12 a is advanced, its outflow apertures 28 may bepositioned at a subdural location within the body of the optic nerve ON(as shown in FIG. 2B) or within the subarachnoid space adjacent to theoptic nerve ON (as shown in FIG. 2C). In instances where the outflowapertures 28 are positioned within the body of the optic nerve ON (asshown in FIG. 2B), fluid that drains out of the outflow apertures 28will subsequently diffuse and/or be transported though the optic nerveand into the subarachnoid space where it will mix with cerebrospinalfluid. In instances where the outflow apertures are located within thesubarachnoid space, fluid that flows out of the outflow apertures 28will mix with cerebrospinal fluid that resides within the subarachnoidspace. In either case, the typical backpressure of fluid adjacent to theoutflow apertures 28 will be low enough to facilitate drainage of excessfluid from the eye and in the distal direction (arrow DD) through theshunt device 12 or 12 a.

[0034] The foregoing description is directed to certain embodiments andexamples of the invention only and does not necessarily include orexpressly mention each and every possible embodiment or example of theinvention that is within the scope of the following claims.

What is claimed is:
 1. A method for draining fluid from the posteriorchamber of the eye of a human or veterinary patient, said methodcomprising the step of: A. creating a passageway between the posteriorchamber of the eye and either i) a location within the optic nerve orii) a location within the subarachnoid space.
 2. A method according toclaim 1 wherein Step A is carried out by implanting a tubular shunt suchthat fluid from the interior of the eye will enter one end of the shuntand said fluid will exit the other end of the shunt either i) at alocation within the optic nerve or ii) at a location within thesubarachnoid space.
 3. A method according to claim 2 wherein the shuntcomprises a tube having a proximal end, a distal end and least onetissue engaging member formed on the shunt to deter unwanted movement ofthe shunt after it has been implanted.
 4. A method according to claim 3wherein the at least one tissue engaging member comprises a barb or barblike structure that allows the shunt to be advanced through tissue in adistal direction but engages the tissue in a manner that deterssubsequent retraction of the shunt in a proximal direction.
 5. A methodaccording to claim 2 wherein the shunt comprises a tube having aproximal end, a distal end and a flange member formed on the proximalend thereof.
 6. A method according to claim 2 wherein the shuntcomprises a tube having a valve associated therewith, said valve beingoperative to perform at least one valving function selected from thegroup consisting of a) allowing fluid to flow out of the eye butdeterring fluid form backflowing into the eye and b) allowing fluid toflow out of the eye only when the fluid pressure exceeds a predeterminedmaximum pressure.
 7. A method according to claim 2 wherein the shuntcomprises a tube having a proximal end, a distal end and at least oneshielding member associated therewith to deter foreign matter or cellsfrom clogging the tube.
 8. A method according to claim 7 wherein theshielding member comprises a semi-permeable membrane constructed andpositioned such that fluid flowing out of the distal end of the tubewill diffuse outwardly through the membrane but foreign matter and cellswill not diffuse inwardly through the membrane and into the distal endof the tube.
 9. A method according to claim 1 wherein Step A comprisesforming an opening in the lamina cribosa.
 10. A method according toclaim 2 wherein the shunt comprises a tube having a distal tip that isconfigured to penetrate through tissue.
 11. A method according to claim1 wherein the method further comprises the performance of a vitrectomyprocedure prior to, concurrently with or after the performance of StepA.
 12. A method according to claim 1 wherein the method furthercomprises liquefaction of at least a portion of the vitreous humor priorto, concurrently with or after the performance of Step A.
 13. A methodaccording to claim 12 wherein liquefaction of at least a portion of thevitreous humor is accomplished by administering to the patient atherapeutically effective amount of an agent that causes vitrealliquefaction.
 14. A method according to claim 13 wherein the agent thatcauses vitreal liquefaction is selected from the group consisting of:urea; urea derivatives; compounds having urea groups; hyaluronidase; andother enzymes that cause vitreal liquefaction.
 15. A method according toclaim 2 wherein Step A further comprises: forming an opening in the parsplana; advancing the shunt through the pars plana opening, through theposterior chamber of the eye and into the optic nerve or lamina cribosa.16. A method according to claim 15 wherein the shunt has a proximalopening, a distal opening and a lumen and wherein the shunt is advancedto a location where its proximal opening is positioned so as to receivefluid from the posterior chamber of the eye and its distal opening ispositioned to allow said fluid to drain into the optic nerve orsubarachnoid space.
 17. A method according to claim 2 wherein the shuntis initially positioned within a cannula that has an open distal end andwherein Step A comprises: inserting the cannula into the eye;positioning the distal end of the canula adjacent to the lamina cribosa;advancing the shunt from the cannula into the optic nerve; and removingthe cannula while leaving the shunt implanted within the eye such thatthe shunt will drain fluid from the posterior chamber of the eye intoeither the optic nerve or the subarachnoid space.
 18. A method accordingto claim 17 wherein a pusher is positioned in the cannula behind theshunt and wherein the step of advancing the shunt from the cannula intothe optic nerve comprises advancing the pusher so as to push the shuntout of the open distal end of the cannula.
 19. A method according toclaim 2 wherein the shunt device is configured to extend through thevitreous body such that aqueous humor will drain through the shunt andinto either the optic nerve or the subarachnoid space.
 20. A methodaccording to claim 2 wherein the shunt is configured to bypass theposterior chamber and vitreous cavity of the eye.
 21. A method accordingto claim 20 wherein the shunt device extends through a subconjunctivalor subscleral tunnel.
 22. A shunt device for draining fluid from theposterior chamber of the eye into the optic nerve or subarachnoid space,said device comprising: a tube having a proximal end, a distal end and alumen extending longitudinally therethrough; a substantially conical tipmember on the distal end of the tube; a plurality of openings formed inthe substantially conical tip member to allow fluid to drain out of thelumen of the tube; and at least one tissue engaging member configured toallow the shunt to be advanced, tip member first, into tissue but toengage said tissue in such a manner as to subsequently deter retractionof the shunt out of the tissue.
 23. A shunt device according to claim 22further comprising a one way valve that allows fluid to flow in only onedirection through the lumen of the tube.
 24. A shunt device according toclaim 22 further comprising a shielding member which deters foreignmatter or cells from clogging the tube.
 25. A shunt device according toclaim 24 wherein the shielding member comprises a semi-permeablemembrane constructed and positioned such that fluid flowing out of theopenings formed in the tip member will diffuse outwardly through themembrane but foreign matter and cells will not diffuse inwardly throughthe membrane and into the lumen of the tube.
 26. A shunt deviceaccording to claim 22 further comprising a flange member on the proximalend of the tube.
 27. A shunt device according to claim 22 that is atleast partially formed of material selected from the group consistingof: silicon; polyethylene; polypropylene; polycarbonate; stainlesssteel; and other biologically compatible material.
 28. A shunt deviceaccording to claim 22 wherein the tube is configured to extend throughthe vitreous body, thereby providing for drainage of aqueous humorthrough the vireous body and into either the optic nerve or thesubarachnoid space.
 29. A shunt device according to claim 22 wherein thetube is configured to extend through a subconjunctival or subscleraltunnel, thereby bypassing the posterior chamber and vireous cavity. 30.A system comprising a shunt device according to claim 22 in combinationwith a cannula, said shunt device being initially positioned within thecannula and subsequently advanceable out of the cannula.
 31. A systemaccording to claim 30 further comprising a pusher that is insertableinto the cannula to push the shunt device out of the cannula.